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FOAMED ASPHALT

Ammann does not focus on a particular method of introducing additives or foam bitumen because many more variables must be considered. The entire process chain is affected, starting with drying at a reduced temperature, continuing through to specific mixing sequences and including the introduction of recycled materials.

Benefits

Lower manufacturing costs

A safer working environment for road crews

Reduced emissions at the jobsite

Lower emission of CO₂ at the plant

No need for new paving equipment; the same pavers and rollers are used

TENDERS

Foamed asphalt meets the quality requirements for hot-mix aggregate. The asphalt specifications and the paved layer remain the same. By observing the recommended procedures the same laboratory tests and processes can be used.

Many countries are now working on national projects aimed at incorporating low-temperature asphalt into the standards. Until they have been adopted, it is important to verify that work tenders explicitly state that use of low-temperature asphalt is permitted.

Low-temperature asphalt production is perfectly compatible with the use of reclaimed asphalt, because the lower mixing temperatures cause less oxidation of the bitumen contained in the RA. Since there is also less aging of the fresh bitumen during the mixing process, improved low-temperature behaviour can be expected from the blacktop.

Foamed bitumen is also used to aid paving in certain countries because it can increase the compactability of the asphalt.

Benefits

Same product quality as hot asphalt

Same recipes as those used for hot asphalt

Same user guidelines as for hot asphalt

Same testing procedures

Fewer emissions on the jobsite

Lower C0₂ emissions at plant

Significantly less fuel consumption

PAVING

The differences between warm and traditional mixes become apparent during placement of the asphalt.

The paving and compaction process changes depending on the low - temperature technology applied. For example, the foam - based mix is compactable for a longer period, while wax - based mixes harden quickly.

Conditions for paving crews are improved, with significantly reduced bitumen vapours and odours. A reduction in the asphalt temperature by 10° C typically cuts in half the emissions on a construction site. This means that a 50° C reduction reduces the emissions by around 95 per cent.

Benefits

Same product quality as hot asphalt

Lower emissions at the construction site

Lower emission of CO₂ at the plant

No need for new paving equipment; the same pavers and rollers are used

MANUFACTURING

Ammann is convinced that the future lies with low temperature asphalt. In cooperation with customers and laboratories, we have developed the Ammann Foam process.

This process is based on the foaming of bitumen with water and is employed in continuous and batch plants. Ammann Foam works without any chemical additives and also can be retrofitted to existing plants with minimal effort.

The process begins when hot bitumen is pumped into the foam generator. Cold water with no chemical additive is injected under high pressure and mixed with the hot bitumen. This water/bitumen mix is then forced through the outlet. The water expands when the mix leaves the foam generator, and the so -called foam bitumen is created.

Benefits

Heating of the raw aggregate to approximately 115 ° C

Perfect mix of bitumen and aggregates

Asphalt compaction at low temperatures

Foam generator can be integrated into continuous and batch plants

Retrofitting to existing plants is possible

FOAM GENERATOR

A foam bitumen installation enables expansion of your plant’s product portfolio. The foam generator from Ammann enables the foaming of various hardnesses of road construction bitumen and also polymer-modified bitumen.

The foam generator also can be used to manufacture cold base courses with 100 per cent recycled materials. This means that the use of foam bitumen optimally supplements the recycling feed in the mixer.

DISCONTINUOUS PROCESS (BATCH)

In the first phase of mixing, the rough granular aggregate is placed in the mixer. The foamed bitumen is introduced into the twin-shaft paddle mixer through the nozzle so that it also coats the rough granular aggregate at about 100° C. The remaining aggregate and filler is then introduced into the mixer.

CONTINUOUS PROCESS

The foamed bitumen is introduced into the mixer together with the aggregate at a temperature of about 100° C. The intensive mixing action of the twin-shaft paddle mixer, which operates continuously, ensures excellent coating of all granular aggregate.

CREDENTIALS

HANS WEIBEL AG, FOAM PROCESS

1500 TONNES OF LOW-TEMPERATURE ASPHALT FOR SWISS ROADS

In 2010, Hans Weibel AG laid 1,500 tonnes of low - temperature asphalt on the basis of the WAM Foam ® process on the busy cantonal road near Koppigen in the Swiss region of Emmental. The ACT 22 N W - ecophalt ® that was used was installed as a base and wearing course.

The asphalt was produced 40 kilometres away in Oberwangen. The Universal NG 320 asphalt mixing plant with warm reclaimed asphalt feed has a dual - row mixing tower, a 4 - tonne Amix mixer and a foamed bitumen installation for the production of low - temperature asphalt.

The advantages of using the new kind of asphalt became apparent as soon as installation started : It reached the construction site at a temperature of around 110°C and was compacted using an AV 95 - 2 at temperatures below 80°C. Working on the construction site was therefore comfortable despite high summer temperatures because of reduced bitumen vapours and substantially less heat radiating from the asphalt.

The asphalt surface demonstrated the required degree of compaction at every measured point despite the demanding logistical situation, as a drill core analysis revealed. Road marking work began shortly after the last pass of the roller to enable the release of the road to traffic the next morning.

CAMANDONA SA INSTALLS A FOAM GENERATOR

RETROFITTING AN ASPHALT MIXING PLANT

About 8,000 m² of low - temperature asphalt has been laid on the parking area at the headquarters of an international corporation near Lausanne, Switzerland. Apart from foamed bitumen technology, this project also made use of Ammannʹs recycling addition system with 40 per cent reclaimed asphalt.

In the low - temperature production process using Ammann Foam, conventional bitumen is foamed with a very small quantity of water. This ensures the same aggregate coating as is achieved with hot mix asphalt.

Foamed bitumen makes it possible to reduce the asphalt production temperature to about 115 ° C. The key benefits : lower energy consumption, less CO₂ at the plant and vastly reduced emissions on the road-building site.

Low - temperature asphalts based on foamed bitumen can be laid in the same way as conventional hot mix. Most importantly, the on - site compaction temperature can also be lowered, leaving sufficient time to achieve good compaction.

The asphalt mixing plant dating from the 1990 s was retrofitted with an Ammann foam generator. The foam generator is entirely integrated into the plantʹs as1 Control System. In addition to the foam generator, the plant at Daillens also features a reclaimed asphalt dryer with variable rotation speeds. This ensures that the exhaust gases do not condense, and that the filter reaches its target performance – even at lower production temperatures.

BERAG AG, FOAMED BITUMEN ASPHALT ON SWISS ROADS FOAMED ASPHALT

IN THE SWISS MOUNTAINS

Starting position
Old gravel roads require substantial and costly maintenance. The access roads to the farms of Andreas Kilcher and Christian Zbinden were no exception.

The construction of two asphalt roads in collaboration with engineering company Keller AG was approved following an inspection by the department for structural improvements and production of the Bernese authority for agriculture and nature. The asphalt used was produced by means of environmental friendly Ammann Foam technology.

The „Studerli” farm
It was indeed a challenge. Christian ¬Zbinden’s farm is located in the middle of a hill in Sangernboden. The serpentine - like road has quite an incline to it. Project scheduling had to take various factors into account, including cattle driving as the farmer drives his herd up to the Alps in the summer. „Things are quieter on the farm after that”, says the farmer. And therefore an ideal opportunity to build an asphalt road.

The „Ottenleuebad” farm
As Andreas Kilcher’s cows were driven to the Alps a week earlier, construction company Walo Bertschinger AG began working on his farm first. The task was to lay asphalt on the access road and the courtyard. Andreas Kilcher and his wife knew exactly how they wanted their farm to look. That is why asphalt was laid all the way to the terrace. The challenge here lay in the fact that the asphalt around the courtyard had to be laid by hand due to spatial constraints. But that wasn’t a problem, either.

Blacktop that is twice as environmentally friendly
An environmentally friendly blacktop on the basis of Ammann Foam was used for both of the roads. The ACT 22 L blacktop with foamed bitumen stands out because it is produced at a temperature of around just 115 ° C and can be laid at even lower temperatures. A normal bitumen of type B160/220 was foamed at the Universal S asphalt mixing plant in Rubigen.

The process produced around 750 kg fewer CO₂ emissions thanks to the drop in temperature alone. But that wasn’t all: the blacktop was made using around 50 per cent reclaimed asphalt. Keeping the asphalt temperature at a constant 115° C was easy thanks to a combined feed of hot and cold reclaimed asphalt.

The blacktop composition matched the specifications exactly. This was made possible by modern plant technology and the Ammann as1 control software.

The result is indeed impressive. The blacktop surface is smooth and the finished composition meets the required quality specifications. By the end of the project 150 tonnes, or 2,000 m2, of blacktop were installed on each farm without a trace of on-site emissions thanks to the low installation temperature.

STATEMENTS

OPINIONS ON LOW-TEMPERATURE ASPHALT

STATEMENTS PRINCIPAL

The authority only defines the width oft he road and the thickness of the layer. The used mix should be “mix used” has to match defined technical criteria, this is our instruction. But we do not tell the contractor how he has to match those criteria. If we can also use more reclaimed asphalt in conjunction with low-temperature asphalt and lower the temperature during production and installation then all the better. Access roads like these are subject to a lot of strain. In Switzerland the maximum load per axle is 11,5 tons distributed on two wheels. The farmers usually drive their machines along the same tracks. This results in depressions similar to those on highways that cause aquaplaning, etc. This is another aspect where blacktops for access roads need to demonstrate a certain stability.

Hans Büttikofer, department for structural improvements and production of the Bernese authority for agriculture and nature.

STATEMENTS BY PAVING COMPANIES

We have established that the blacktop can be installed and compacted using conventional methods. If it can be installed on this difficult terrain it can be installed anywhere.

STATEMENTS BY PLANT OWNERS

Low - temperature surfaces are the way ahead ! The use of foamed bitumen technology enables us to achieve energy savings of 1.5 kg of fuel oil per tonne of asphalt. We were able to save around 7.5 tonnes of CO₂ emissions during the installation work at Koppingen and therefore make a contribution towards sustainable road construction. There are no problems with the quality of the asphalt mix produced and it meets every requirement of the applicable standard both at the plant and after installation. The installation work at Koppingen was a positive and promising experience. We are convinced that low - temperature surfaces will prove to be ground-breaking for the asphalt and road building industry.

STATEMENTS BY THE LAB

Taking care of our environment is an important aspect in my opinion. Every method that contributes towards that goal is important. In our laboratories we examine the mixes produced by the mixing plants. Our production analyses show no differences to hot asphalt with regard to compaction, porosity, lifetime, smoothness, etc. Both are equally as good and comparable. I am convinced that foamed bitumen is the right way ahead and a good path to follow because it saves energy. One should not forget that the mix is 30–40 ° Celsius cooler than a hot asphalt mix. And these 30–40 ° are pure oil that otherwise needs to be combusted.

STATEMENTS BY PLANT MANUFACTURER

An asphalt mixing plant uses the most energy when it heats up the aggregate. If we can manage to reduce the temperature we can provide a major contribution towards reducing costs and the consumption of resources.

AMMANN GROUP

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